JPS64475B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a steel sheet for fuel containers that exhibits excellent performance in corrosion resistance, workability, and weldability that are optimal for containers containing alcohol fuel and alcohol-containing gasoline fuel. (Prior Art and Problems to be Solved by the Invention) With the recent deterioration of the oil situation (rise in oil costs and decrease in production), gasoline such as methyl alcohol and ethyl alcohol are being used as automobile fuels. Methyl alcohol, ethyl alcohol, methyl tert-butyl alcohol (MTBA) for alcohol fuel or gasoline
The use of fuel mixed with alcohol (so-called gasohol) as an alternative fuel has been proposed and is being put into practice. Materials for automobile fuel containers for these alcohol fuels or alcohol-added gasoline (gasohol) include Pb-, which has been announced in many patent publications such as JP-A-50-23345 and JP-A-51-115240.
Although Sn alloy coated steel sheets have been used, there has been a problem in that the corrosion resistance of the steel sheets has been significantly degraded. In other words, the reason for this is that the coating layer of Pb-Sn alloy steel sheets is composed of a eutectic alloy of Pb and Sn, which is mainly composed of Pb.For example, (a) Pb metal is severely corroded by methyl alcohol. Therefore, the Pb metal layer of the coating layer is easily corroded. (b) Pb metal is significantly corroded by acetaldehyde, acetic acid (an oxidation product of ethyl alcohol), formaldehyde, or formic acid (an oxidation product of methyl alcohol) produced when alcohol fuel or alcohol-added gasoline is oxidized. The Pb metal layer in the coating layer is easily corroded. (c) Moisture contained in alcohol or oxidation products of alcohol increase corrosion from pinholes formed in the coating layer. Due to these reasons, the corrosion resistance of Pb-Sn and alloy plated steel sheets is significantly deteriorated. For this reason, a highly corrosion-resistant material is required as a container steel plate for storing such fuel, which has few pinholes in the coating layer and has excellent corrosion resistance against alcohol and alcohol oxidation products. Furthermore, depending on the processed shape of the fuel container or the high-speed molding method, the pinholes in the coating layer may expand,
There are phenomena in which problems such as the generation of red rust from these defects occur due to the formation of defects that reach the base steel due to scratches in the coating layer due to the "press scuffing" phenomenon on the surface, and the generation of defects that reach the base steel during handling. It was done.
In particular, corrosion progressed due to large amounts of Cl ^- ions, moisture, etc. mixed in from gasoline or from the outside, or due to moisture separated from a mixed fuel of alcohol and gasoline, and there was a risk of perforation due to perforation corrosion.
On the other hand, the problem of corrosion caused by snow melting salt on the outer surface of the tank has become more severe in recent years, and as mentioned above, damage caused by defects in the coating layer or collisions with road-sprayed salt (so-called
There is a concern that corrosion caused by Cl ^- ions, especially perforation corrosion that leads to perforations, may occur due to the occurrence of flaws that reach the base steel due to the chipping phenomenon. (Means for solving the problem and operation and effects of the invention) The present invention was made in response to these situations.
Problems and tanks regarding corrosion resistance of plating-coated steel sheets made of Ni, Co, Sn, alloys thereof, and alloys containing one or more of P, Mo, and Cr to alcohol fuels, alcohol-containing fuels, gasoline, etc. In addition to solving the problem of corrosion from snow melting salt on the outer surface, it also improves moldability and
The purpose is to provide a steel plate for fuel containers that has excellent weldability. That is, the gist of the present invention is as follows: C: 0.02% or less Cr: 3 to 20% Acid-soluble Al: 0.005 to 0.10% If necessary, one or more of Ti, Nb, Zr, and V Ni, Sn, Co, and alloys thereof, or alloys containing one or more of P, Mo, and Cr on at least one side of a steel plate containing 0.03 to 0.5% of each, and the balance being unavoidable impurities and iron. This is a steel plate for alcohol or alcohol-containing fuel containers with a plating coating layer. The present invention will be explained in detail below. Steel sheets containing 3% or more Cr, especially 5% or more,
Shows excellent corrosion resistance to alcohol, fuel containing alcohol, gasoline, oxidation products of alcohol (aldehydes, organic acids such as formic acid and saccharic acid), and gasoline. However, when the Cr content exceeds 20%,
This is not preferable because it deteriorates workability and weldability, making it difficult to form or weld the fuel container. Therefore, from the viewpoint of corrosion resistance against red rust of the above-mentioned corrosion products, workability, and weldability, the Cr content should be set at 3 to 3.
It was defined to be 20%, preferably in the range of 5 to 15%. As mentioned above, from the point of view of corrosion resistance, Cr has the greatest effect, but in this invention, from the viewpoint of targeting fuel tank materials for automobiles and other storage, the content of C acid-soluble Al and other steel components is also included. Limit quantity. As the C content increases, chromium carbide is precipitated and the mechanical properties and corrosion resistance of steel deteriorate. Therefore, the C content is 0.02% or less, preferably
Desirably 0.005% or less. Al is the amount of acid-soluble Al (SolAl) remaining in the steel.
At a low content of less than 0.005%, it is difficult to prevent the generation of bubbles due to oxygen gas, which significantly increases the incidence of surface defects in steel and becomes the starting point for deterioration of the corrosion resistance of steel materials. In addition, excess acid-soluble Al exceeding 0.10%
In this method, Al-based oxides are scattered on the steel surface, which is the starting point for deterioration of corrosion resistance, or causes defects, pinholes, etc. on the plating surface applied to the steel sheet, impairing the plating integrity. Moreover, in the present invention, the second
invention, in addition to the above steel components, 0.03 to 0.50%
The steel contains one or more of Ti, Nb, Zr, and V to combine with C in the steel to make the Cr contained in the steel more effective, further improving formability and corrosion resistance. . When the content of steel components such as Ti is less than 0.03%, the effect of preventing chromium carbide precipitation and improving formability and corrosion resistance is small, and when the content exceeds 0.50%, the effect reaches saturation. In addition to being uneconomical, precipitation of these components tends to harden the material and deteriorate moldability. In particular, preferably the content of these elements is 0.075
~0.20% range. In the present invention, if such steel plates are used as they are for fuel containers, the corrosion resistance is insufficient, so these steel plates are treated with Ni, Co, Sn, alloys thereof, and one of P, Mo, and Cr for these steel plates. An alloy containing a species or two or more species is plated. In other words, if the above-mentioned steel sheet is used as it is, the inner surface of the fuel container will not have sufficient corrosion resistance against water, Cl ^- ions, etc. contained in the fuel, and the corrosion resistance of the outer surface of the fuel container will be greater than that of the outer surface of the fuel container. moisture,
Due to the corrosive atmosphere containing a large amount of Cl ^- ions, red rust occurs significantly, and the reduction in plate thickness (corrosion amount) increases significantly, resulting in insufficient corrosion resistance. Therefore,
In order to solve these problems, the present invention provides a coating layer of metal or alloy that has good corrosion resistance against alcohol, alcohol-containing fuel, alcohol oxidation products, moisture, gasoline Cl ^- ions, etc. Therefore, the purpose is to ensure corrosion resistance, and also to ensure corrosion resistance of the steel base, such as defects (pinholes) in the coating layer and scratches on the base steel during forming processing. In addition, by using the Cr-containing steel composition and coating layer of the present invention,
, Ni plate 1 is the anode, (+) is Cr steel 2 is the anode, 3 is 1
% NaCl solution), the effect of reducing the couple corrosion current between the steel base and the coating layer allows the coating layer to remain intact even if there are defects in the coating layer such as pinholes or flaws that occur during forming. If the potential is more base than the steel base, the amount of corrosion due to the sacrificial corrosion protection of the coating layer will be small, and even if the coating layer is potential more noble than the steel base, the amount of corrosion of the steel base will be small. , the risk of drilling corrosion is extremely low. As a result, the coating amount (plating amount) of the coating layer of the present invention can be reduced (thinned), resulting in extremely excellent adhesion of the coating layer and moldability, which is particularly required for fuel containers. Effects can be obtained. Therefore, in the present invention, Ni, Sn, Co, alloys thereof, or alloys thereof, which have good corrosion resistance against alcohol, alcohol-containing fuel, alcohol oxidation products (aldehydes, organic acids), gasoline, moisture, and Cl ^- ions, are used. An alloy coating layer containing one or more of P, Mo, and Cr is applied to the metal. The coating treatment method, coating treatment conditions, etc. are not particularly specified, but after surface cleaning and activation treatment of the Cr-containing steel plate such as degreasing and pickling, the coating treatment is carried out under the following conditions. It is done. (1) Ni plating bath composition; Nickel sulfate 250g / Nickel chloride 70g / Boric acid 30g / Current density 5 to 150 A/dm ² (2) Sn plating bath composition; Phenolsulfonic acid
20g/Stannic sulfate 60g/ENSA (additive) 10g/(3) Ni-Sn alloy plated nickel chloride 250g/Stannic chloride 50g/Acidic ammonium fluoride 50g/(4) Ni-P alloy plated nickel sulfate 80g / Nickel chloride 30g / Phosphous acid 20g / Phosphoric acid 10g / (5) Ni-Cr alloy Mekki nickel sulfate 260g / Chromium chloride 53g / Glycine 20g / Ammonium chloride 200g / (6) Co-Mo alloy Mekki cobalt sulfate 85g / Citrus Sodium acid 88g / Sodium molybdate 40g / (7) Ni-Co-P alloy plating Cobalt sulfate 30g / Nickel sulfate 50g / Nickel chloride 30g / Phosphorous acid 20g / Phosphoric acid 10g / Such a plating layer has a coating thickness of 0.1~ It is applied in a thickness of 10μ, particularly preferably a thickness of 0.5 to 5μ.
This is because if the thickness is less than 0.1 μm, the uniform coverage of the coating layer is extremely insufficient, a large amount of pinholes are generated, and the effect of improving corrosion resistance may not be obtained. Further, if the thickness of the coating layer exceeds 10 μm, the effect of improving corrosion resistance is saturated and the adhesion and moldability of the coating layer tend to deteriorate, which is not preferable. In addition, regarding the alloy composition of the coating layer, Ni, Sn,
When combined with Co, each metal exhibits almost the same excellent corrosion resistance, and a full range of alloy compositions are used. On the other hand, in the case of alloying one or more of P, Mo, and Cr contained in these metal alloys,
The preferred amount of alloying is selected for each of the following reasons. In other words, when Ni, Sn, Co, and their alloys are alloyed with more than 40% of P and Mo, and when more than 30% of Cr is alloyed,
Each of them hardens the coating layer and deteriorates the adhesion and moldability of the coating layer, which is undesirable from the viewpoint of electrolytic efficiency in electroplating work. Therefore, P,
When an alloyed coating layer of Mo and Cr is provided, P and Mo are 40% or less, preferably 20% or less, and Cr is
It is better to use a content of less than 30%, preferably less than 15%. Further, when two or more of these are alloyed, it is preferable that the alloying elements be selected so that the total sum of the alloying elements to be combined falls within the maximum allowable amount of the alloying elements used. For example, P+
Mo; 40% or less, P+Cr; 30% or less, Mo+Cr;
30% or less, P + Mo + Cr: By suppressing it within the range of 30% or less, the corrosion resistance of the coating layer is further improved,
Corrosion resistance life is extended. Furthermore, the surface of the coating layer of the present invention may be subjected to a chromate-based treatment for the purpose of improving the corrosion resistance or painting performance of these coating layers, and in particular extending the corrosion-resistant life of the coating on the outer surface of the fuel container. good. For chromate treatment, use CrO ₃ aqueous solution or CrO ₃
CrO ₃ −SO ₄ ⁻² , CrO ₃ − with anion added to
This is carried out by immersion treatment using a PO ₄ ^-2 , CrO ₃ -F ^- based bath, electrolytic treatment, etc. In this case, the present invention:
Since it is composed of a coating layer with stable chemical reactivity, CrO ₃ -SO ₄ ^-2 , which contains anions in CrO ₃ ,
_Cr ^_
A coating with a coating amount of 10 to 150 mg/m ² (per side) has excellent effects (improved corrosion resistance and paintability)
is obtained, which is preferable. Furthermore, the outer surface of the fuel container of the present invention may be coated with a Zn or Zn-based alloy plating layer to provide corrosion protection against corrosion from the outer surface. In other words, Zn or Zn- (8 to 20%), Ni, Zn (8 to 20%), which has relatively good corrosion resistance against Cl ^- ions etc. from road salt, etc., and has a sacrificial corrosion protection effect on steel materials.
~20%) Co, Zn (8~20%) (Ni+Co), Zn−
(8~20%) Apply a Fe-based alloy coating layer of 0.5~10μ,
It may be possible to extend the corrosion resistance life against corrosion from the outside surface. Similarly, the coating treatment of the present invention may be applied to both surfaces, and the outer surface may be subjected to a chromate treatment as described above to provide a coating treatment that serves both as corrosion prevention and decoration. Further, if the corrosive environment is mild against external corrosion, the coating layer of the present invention may be applied only to the inner surface of the fuel container, and the outer surface may be used as it is made of steel. As described above, according to the present invention, as an alcohol or alcohol-containing fuel tank steel sheet for automobiles, etc., due to the mutual effects of the steel composition and the coating layer of the present invention, it has extremely excellent corrosion resistance and formability, and also has excellent weldability. Therefore, it is possible to provide a steel plate for fuel containers that can be secured. Although the steel components of the present invention are specified as described above, even if Ni, Mo, etc. are contained in these steels as impurities from converters, etc., at 1% or less and 0.3% or less, respectively, the performance will not be affected. The impact is small. Furthermore, at the same time, the present invention has been described regarding alcohol or a fuel tank containing alcohol;
Even if it is applied to or shared with a fuel tank intended for ordinary gasoline, its corrosion resistance is good and there is no problem. (Example) Examples of the present invention will be described below. A steel plate with a steel composition whose Cr content is mainly changed is used, and after degreasing and pickling, it is subjected to normal electroplating pretreatment, and then a predetermined amount of the coating layer of the present invention is applied to at least one side of the steel plate. Regarding the steel plate of the present invention, performance evaluations were performed on the outer surface and inner surface of the tank, respectively, for a rectangular cylinder drawing material assuming the shape of a tank. As a result, the product of the present invention has extremely superior properties as a steel sheet for alcohol or alcohol-containing fuel containers, compared to comparative materials. The evaluation test was conducted in the following manner. 1 Evaluation test for the inner surface of the tank (A) Test for gasohol {84.5% gasoline + 15% methanol + 0.2%
Formic acid + 1% NaCl aqueous solution containing 0.3%} system solution (B) Gasohol target test {79.8% gasoline + 19% ethanol + 0.2%
citric acid + 1% distilled water} solution (C) Gasohol target test {82.49% gasoline + 7.5% methanol + 0.01
% formic acid}-based solution (D) 100% alcohol test {contains 4.7% of 95% methanol + 0.2% formic acid + 0.1% formaldehyde + 1% NaCl aqueous solution}
Using each aqueous solution in the system, a rectangular cylindrical drawing test piece with a height of 200 x 200 mm x 80 mm was created from a blank size of 500 x 500 mm, the inside of the test piece was filled with the above corrosive solution and sealed, and vibrated for about 1 year. This was repeated and the internal corrosion status was determined. 2 Evaluation test of tank outer surface (E) Cycle corrosion test Salt water spray (5% NaCl 35℃ x 4 hours) →
Dry (70℃ humidity 60% 2 hours) → Humidity (49℃
Humidity 98% for 2 hours) → Cooling (-20℃ x 2 hours) → Salt water spray - 1 cycle The above cycle was repeated 35 times, and the reduction in plate thickness in corroded areas and the occurrence of rust were comprehensively evaluated, and the corrosion resistance was evaluated. The performance was evaluated. Incidentally, the surface corresponding to the outer surface of the fuel container of the present invention is
Performance evaluation was performed on chromate treatment of 18.7 mg/m ² by cathodic electrolysis treatment of 10 A/dm ² -1 second using 100 g/CrO ₃ -0.6 g/m ² SO ₄ ^-2 bath. I did it. (F) Corrosion resistance test after painting Using the evaluation material treated with chromate from the evaluation test (E) above, the epoxy
Approximately 7.5mm in diameter after painting with 25μ of phenol paint
After chipping fine stones with a diameter of 3.5 μg/cm ² for 10 seconds so that 2 g per 1 cm ² collided with each other, a test was conducted for 30 cycles under the cycle test conditions (E) above, and red rust was observed from the chipping area. Corrosion resistance after painting was evaluated based on the situation, measurement of plate thickness reduction in that area, and occurrence of blisters on the painted surface other than the chipping area. 3 Formability evaluation test Blank size 0.8 x 500 x 500 mm, after applying lubricating oil, square tube drawing was performed with a 150 x 150 mm square punch under the conditions of wrinkle pressing pressure 30T, and the limit of drawing depth and square tube drawing material / outer surface The moldability was evaluated based on the occurrence of galling and the peeling of powdery coating layer (powdering phenomenon).

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[Table] (Note) Judgment criteria: ◎ Extremely good ○ Relatively good △ Slightly poor × Significantly poor

[Brief explanation of drawings]

FIG. 1 is a graph showing the current flowing when a steel plate and a nickel plate having different chromium contents are combined and immersed in a 1% NaCl aqueous solution in relation to the amount of Cr in the steel. 1: Ni plate, 2: Cr steel, 3: 1% NaCl solution.

[Claims]

1: a cylindrical device case with one end open; a hollow shaft rotatably supported on the other end wall of the device case, with a free end extending into the device case, and a hole bored in the peripheral wall; an insoluble anode and a plating liquid stirring blade disposed on the circumferential surface of the hollow shaft; a plating liquid supply means for supplying the plating liquid into the apparatus case through the hollow shaft; and a plating liquid supply means for supplying the plating liquid into the apparatus case. A pipe end plating device comprising: a plating liquid discharge means for discharging the liquid to the outside; and a means for rotating the hollow shaft.

Claims (1)

3% by weight, C: 0.02% or less, Cr: 3 to 20%, acid-soluble Al: 0.005 to 0.10%, and the remainder is iron and unavoidable impurities. At least one side of the steel plate is coated with Ni, Sn, and Co. One or two of P, Mo, and Cr are added to metals or their alloys.
1. A steel sheet for use in alcohol or alcohol-containing fuel containers, characterized in that it is coated with an alloy plating layer containing at least 100% of alcohol. 4% by weight, C: 0.02% or less, Cr: 3-20%, acid-soluble Al: 0.005-0.10%, and further contains 0.03-0.5% each of one or more of Ti, Nb, Zr, and V. At least one side of a steel plate, the remainder of which is iron and unavoidable impurities, is coated with metals such as Ni, Sn, and Co, or alloys thereof, and one or both of P, Mo, and Cr.
1. A steel sheet for use in alcohol or alcohol-containing fuel containers, characterized in that it is coated with an alloy plating layer containing at least 100% of alcohol.